A study was made of the affinity of mescaline, methedrine, LAE and LSD for fibrous wool protein. The order of increasing affinity was mescaline, methedrine, LAE, and LSD, indicating that the higher the affinity for wool, the smaller the amount required to produce a psychotic effect. The author speculates on the relationship between chemical structure and biological activity, and the factors aggravating and preventing the psychotic effects of drugs. In this connection, he points out that pre-treatment with methylene blue (0.15 mcg. intragluteally) reduced the intensity of symptoms after 80 mcg. of LSD approximately 40%. To date, the most effective agent for preventing LSD symptoms is diparcol.